THE PRODUCTION OF CLEAN MILK. 



By Prof. H. D. Evans, State Laboratory of Hygiene. 



In these days of comparative enlightenment it hardly would 

 seem necessary to speak of the importance of clean milk. The 

 experience of all, who have had to do with the control of our 

 milk supplies, does, however, show a very real need of more 

 knowledge and care on the part of our milk producers. Thus 

 it is not out of place this evening to call to the attention of 

 both producers and consumers the need of cleanliness in milk 

 and its products ; and to briefly indicate both what this dirty 

 milk means from a health standpoint, and how the condition 

 can be remedied, at least to a large extent. 



The dictionary tells us that "any foreign substance in, or 

 on a material" is "dirt." This is a broad definition, and, under 

 it. watered, colored or preserved milk would have to be con- 

 sidered as dirty. The word dirt calls to our minds some such 

 thing as mud, sand, or organic refuse, and dirty milk is gen- 

 erally thought of as contaminated with such substances. In 

 this discussion I shall not consider as "dirt" substances delib- 

 erately added to milk, as water, coloring matters and preserva- 

 tives, but shall confine the consideration to the visible earthy and 

 organic matters, together with the invisible dirt attached to it. 

 For this discussion we may class dirt into pJiysical dirt and 

 bacterial dirt. 



Physical dirt, which we find in milk, is such as is visible 

 to the eye. It consists of earthy matters, straw, dust, hair, 

 and manure flakes. It is derived from the cow's body as in 

 the case of hair, dandruff and manure flakes; from the dirt in 

 the stable, as in the case of straw, hay and some of the earthy 

 materials ; and from the air, as in the case of dust. In addition 

 there is the possibility of all kinds of physical dirt entering the 

 milk in the milk room, from dirty utensils, dirty shelves, and 

 being shaken off from dirty employes. 



